The market for telecommunications cable and related products is in an over capacity state. The large number of suppliers of these products has put tremendous pressure on the industry to provide communications cable with increased performance at lower costs.
Rodents cause significant problems in cable environments. Their incessant need to chew in order to control tooth size is relentless. One correctly placed incision by a rodent could destroy an optical fiber and result in the loss of millions of dollars in sales of telecommunications traffic. To date, cable manufacturers have used steel tapes to armor the cable. This steel barrier is highly effective in preventing rodents from breaching the cable. However, it has the same deterring effect on cable installers. The result is not only additional expense in cable manufacturing but also in installation.
In the past, rodent resistant cables have been constructed to include steel tape-wound outer jackets. In other designs, an inner jacket of thermoplastic is overlaid with a corrugated steel tape, the overlap of which is welded to produce a watertight armouring. For example; an outer polyethylene cable jacket is bonded to a polymer coating on the steel armouring enhancing the protection given to the cable against rodents. In other rodent resistant cable designs, the cable is protected by a plurality of spikes, which extend radially outward from an outer jacket, which completely encircles and covers the cable. The use of poisons has also been employed inside cables.
Flexible cable reinforcements are almost always applied around the cable core to provide strength during installation. If these reinforcements could also act to prevent rodents from damaging the optical fibers, costs could dramatically be reduced. The present invention is multi-functional cable reinforcement. First, it provides tensile strength to the cable for installation. Next, it blocks water intrusion with its hydrophobic coating. Further, it acts as a crush resistant layer dispersing the energy of any impact the cable may see. Finally, if a rodent should opt to chew on the cable it will find the irritation from the glass fibers in this product to be unbearable and desist from further chewing.
The large fiber diameter (between about 1 to about 89 microns) of this product acts to enhance the irritation capacity while the coating holds the irritating fibers in place, imbedded in the surface of the rodent's mouth, gums and lips. Finally, the chewy nature of the coating will be tactilely displeasing to the rodent and discourage further chewing.
Optical communications cables consist essentially of a plurality of randomly placed optical communication fibers, typically in ribbon form, contained within a polymer jacket. Of course, other types of communications cables can have single optical fibers, bundled optical fibers, or tight buffered optical fibers. The fibers are typically tight or loose buffered within a polymer tube contained within a portion of the jacket. One or more flexible reinforcement members and stiff strength members may also be contained within a portion of the polymer jacket outside of the central tube or buffer tubes to provide support and prevent kinking of the communication fibers. These reinforcement members are applied by being wrapped helically around the inner core prior to outer jacketing (as in optical loose tube cable types) or are directly extruded into the jacket matrix (as in twisted copper telephone cable).
The flexible reinforcements for cables are made in a wide variety of methods. Typically, these reinforcements are manufactured by first applying a binder and sizing containing a film former and oils or coupling agents to a glass strand and then applying a relatively heavy layer of a water-based, high molecular weight polymer latex or wax. The coated strands may then be introduced to the communications cables by known methods.
These coatings may impart many important properties to the flexible reinforcements both during manufacture and after introduction to the cable. For example, these coatings prevent abrasion of the glass fibers during the combination with the reinforcement and during deployment. Also, these coatings prevent adhesion of the reinforcing fibers to the polymer jacket. These coatings may also impart adhesion if desired to the polymer jacket, for example, as is the case with polyvinyl chloride (PVC) jacketed communications cables. Additionally, these coatings can be super absorbent and can thus prevent water seepage from damaging the optical fibers.